J Korean Soc Radiol.  2009 Sep;61(3):143-148. 10.3348/jksr.2009.61.3.143.

The Effect of Heat Treatment and Mechanical Polishing on Nitinol Stent

• Park S
• Kang SG
• Lee SC
• Kim KS
• Choi SH
• Park CS
• Yoon CJ
• Park JH

• KMID: 2012866
• DOI: http://doi.org/10.3348/jksr.2009.61.3.143

Abstract

PURPOSE
To understand the effect of heat treatment and mechanical polishing of a Nitinol wire on the chemical composition and physical morphology of the wire surface.
MATERIALS AND METHODS
Stents with a diameter of 1.0 cm, length of 8-10 cm, and composed of a Nitinol wire, were heat-treated at 500 degrees for 30 minutes, and mechanically polished with walnut shell granules. The wire surface morphology was studied with both an optical and a scanning electron microscope (SEM). In addition, an elemental analysis was performed by Energy Dispersive X-ray spectroscopy (EDX).
RESULTS
Long microcracks along the wire direction and short microcracks across the wire were observed by SEM from the raw Nitinol wire. Upon heat treatment, the color of the wire turned blue, and Na, K, Cl, Si, Al atoms were seen from the EDX of the heat treated wire, which were absent in the original wire. The microcracks disappeared with the mechanical polishing, and the Na, K, Cl, Si, Al atoms all disappeared after the mechanical polishing.
CONCLUSION
Mechanical polishing using walnut shell granules effectively removed the microcracks of a nitinol wire and impurities produced from the heat treatment.

MeSH Terms

Alloys
Biocompatible Materials
Electrons
Hot Temperature
Juglans
Nickel
Spectrometry, X-Ray Emission
Stents
Surface Properties
Titanium
Alloys
Biocompatible Materials
Nickel
Titanium